The subject matter disclosed herein relates to drive trains. More specifically, the subject disclosure relates to gearboxes for rotary-wing aircraft.
Rotary-wing aircraft require a gearbox to transfer power from the engine or engines to the rotary wing. Since the desired rotational velocity of the rotor is lower than that of the engine, the rotational velocity transferred from the engine to the rotor must be reduced in the gearbox via a gear reduction system. The velocity reduction is accomplished via one or more intermediate gears between the engine and an output gear which drives the rotor. The rotational velocity reduction via these intermediate gears also increases a torque transferred to the output gear, so that the output gear size must be increased to withstand the torque applied. In some rotary-wing aircraft, especially ones with two counter-rotating rotors, the resulting gearbox is large and heavy. For example, some gearboxes for such aircraft have two separate output bull gears, driven by a pair of pinions connected to the bull gears by a spiral bevel mesh. The two bull gears and ancillary components take up considerable space and result in a heavy gearbox. Since both space and weight are at a premium in any aircraft, the art would favorably receive a rotary ring aircraft gearbox which has improvements in size and weight.